Question

A boy is cycling such that the wheels of the cycle are making $140$ revolutions per hour. If the diameter of the wheel is $60cm$ then calculate the speed (in $km/h$) with which the boy is cycling.

Answer 1

The cycle makes $140$ revolutions per hour
Diameter of the wheel $=60cm$
Radius of the wheel $=30cm$
Circumference of a circle $=2\pi r$
$=2\times \frac{22}{7}\times 30$
$=\frac{44\times 30}{7}$
$=188.57cm$
Distance cover in $140$ revolutions
$=140\times 188.57=26400cm\therefore Speed=\frac{26400}{100000}÷1km/h$
$=0.264km/h$ [$\because 1km=100000cm$]